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99 lines
4.1 KiB
SQL
99 lines
4.1 KiB
SQL
-- Copyright (c) 2014, 2015, Oracle and/or its affiliates. All rights reserved.
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--
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-- This program is free software; you can redistribute it and/or modify
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-- it under the terms of the GNU General Public License as published by
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-- the Free Software Foundation; version 2 of the License.
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--
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-- This program is distributed in the hope that it will be useful,
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-- but WITHOUT ANY WARRANTY; without even the implied warranty of
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-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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-- GNU General Public License for more details.
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--
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-- You should have received a copy of the GNU General Public License
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-- along with this program; if not, write to the Free Software
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-- Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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DROP FUNCTION IF EXISTS sys_get_config;
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DELIMITER $$
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CREATE DEFINER='mariadb.sys'@'localhost' FUNCTION sys_get_config (
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in_variable_name VARCHAR(128),
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in_default_value VARCHAR(128)
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)
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RETURNS VARCHAR(128)
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COMMENT '
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Description
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-----------
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Returns the value for the requested variable using the following logic:
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1. If the option exists in sys.sys_config return the value from there.
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2. Else fall back on the provided default value.
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Notes for using sys_get_config():
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* If the default value argument to sys_get_config() is NULL and case 2. is reached, NULL is returned.
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It is then expected that the caller is able to handle NULL for the given configuration option.
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* The convention is to name the user variables @sys.<name of variable>. It is <name of variable> that
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is stored in the sys_config table and is what is expected as the argument to sys_get_config().
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* If you want to check whether the configuration option has already been set and if not assign with
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the return value of sys_get_config() you can use IFNULL(...) (see example below). However this should
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not be done inside a loop (e.g. for each row in a result set) as for repeated calls where assignment
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is only needed in the first iteration using IFNULL(...) is expected to be significantly slower than
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using an IF (...) THEN ... END IF; block (see example below).
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Parameters
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-----------
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in_variable_name (VARCHAR(128)):
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The name of the config option to return the value for.
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in_default_value (VARCHAR(128)):
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The default value to return if the variable does not exist in sys.sys_config.
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Returns
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-----------
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VARCHAR(128)
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Example
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-----------
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-- Get the configuration value from sys.sys_config falling back on 128 if the option is not present in the table.
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mysql> SELECT sys.sys_get_config(''statement_truncate_len'', 128) AS Value;
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+-------+
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| Value |
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+-------+
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| 64 |
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+-------+
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1 row in set (0.00 sec)
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-- Check whether the option is already set, if not assign - IFNULL(...) one liner example.
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mysql> SET @sys.statement_truncate_len = IFNULL(@sys.statement_truncate_len, sys.sys_get_config(''statement_truncate_len'', 64));
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Query OK, 0 rows affected (0.00 sec)
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-- Check whether the option is already set, if not assign - IF ... THEN ... END IF example.
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IF (@sys.statement_truncate_len IS NULL) THEN
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SET @sys.statement_truncate_len = sys.sys_get_config(''statement_truncate_len'', 64);
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END IF;
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'
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SQL SECURITY INVOKER
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DETERMINISTIC
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READS SQL DATA
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BEGIN
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DECLARE v_value VARCHAR(128) DEFAULT NULL;
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DECLARE old_val INTEGER DEFAULT NULL;
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-- Check if we have the variable in the sys.sys_config table
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SET v_value = (SELECT value FROM sys.sys_config WHERE variable = in_variable_name);
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-- Protection against the variable not existing in sys_config
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IF (v_value IS NULL) THEN
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SET v_value = in_default_value;
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END IF;
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RETURN v_value;
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END $$
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DELIMITER ;
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